This application is intended to explore the distribution and role of dynorphin-related oploid pepteides in part of the descending projection from superior olive to cochlea in the chinchilla. The lateral olivecochlear system descends from cells in the lateral superior olive to the cochlea were terminal contact auditory nerve fibers at the base of inner hair cells. This study will use basic imunochemical techniques to establish the distribution of dynorphin-related peptides in the lateral olivocochlear system of the chinchilla brainstem and cochlea. The functional role of these peptides will be explored by recording cochlear compound action potentials during cochlear exposure to a range of dynorphin-related peptides, and antagonists. Peptide administered through the semi-permeable round window membrane. Published and preliminary data by the PI show that an intravenously delivered kappaopiod agonist (- pentazocine) increases the amplitudes of round-window recorded compound action potentials while round window of a k-opoid antagonist (nor- binaltophimine) blocks these effects.